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<textarea name='code' class='java:nogutter' rows='15' cols='120'>
/*
 * SmartGWT (GWT for SmartClient)
 * Copyright 2008 and beyond, Isomorphic Software, Inc.
 *
 * SmartGWT is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License version 3
 * as published by the Free Software Foundation.  SmartGWT is also
 * available under typical commercial license terms - see
 * http://smartclient.com/license
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 */

import com.smartgwt.client.types.Alignment;
import com.smartgwt.client.types.DragAppearance;
import com.smartgwt.client.types.Overflow;
import com.smartgwt.client.types.Visibility;
import com.smartgwt.client.util.EventHandler;
import com.smartgwt.client.widgets.Canvas;
import com.smartgwt.client.widgets.Img;
import com.smartgwt.client.widgets.Label;
import com.smartgwt.client.widgets.events.*;

public class DragEventsSample implements EntryPoint {

    public void onModuleLoad() {
        Canvas canvas = new Canvas();

        final Img img = new Img("pieces/48/pawn_green.png", 48, 48) {
            protected boolean setDragTracker() {
                Canvas c = new Canvas();
                String html = Canvas.imgHTML("pieces/24/pawn_green.png", 24, 24, null, null, null);
                EventHandler.setDragTracker(html);
                return false;
            }
        };
        img.setCanDrag(true);
        img.setCanDrop(true);
        img.setDragAppearance(DragAppearance.TRACKER);

        final DropLabel label = new DropLabel();
        label.setLeft(100);
        label.setWidth(300);
        label.setHeight(300);
        label.setBackgroundColor("lightblue");
        label.setAlign(Alignment.CENTER);
        label.setContents("Show Drop Reticle");
        label.setOverflow(Overflow.HIDDEN);
        label.setCanAcceptDrop(true);

        canvas.addChild(img);
        canvas.addChild(label);
        canvas.draw();
    }

    class DropLabel extends Label {

        private Canvas crossHairX;
        private Canvas crossHairY;

        protected void onInit() {
            crossHairX = createCrossHair();
            crossHairY = createCrossHair();
            addChild(crossHairX);
            addChild(crossHairY);

            this.addDropOverHandler(new DropOverHandler() {
                public void onDropOver(DropOverEvent event) {
                    getCrossHairX().show();
                    getCrossHairY().show();
                    updateCrossHairs();
                }
            });

            this.addDropMoveHandler(new DropMoveHandler() {
                public void onDropMove(DropMoveEvent event) {
                    updateCrossHairs();
                }
            });

            this.addDropOutHandler(new DropOutHandler() {
                public void onDropOut(DropOutEvent event) {
                    getCrossHairX().hide();
                    getCrossHairY().hide();
                }
            });

        }

        private Canvas createCrossHair() {
            Canvas canvas = new Canvas();
            canvas.setWidth(this.getWidth() + 2);
            canvas.setHeight(this.getHeight() + 2);
            canvas.setBorder("1px solid black");
            canvas.setVisibility(Visibility.HIDDEN);
            return canvas;
        }

        public Canvas getCrossHairX() {
            return crossHairX;
        }

        public Canvas getCrossHairY() {
            return crossHairY;
        }

        public void updateCrossHairs() {
            int x = getOffsetX();
            int y = getOffsetY();

            // crossHairX is the -X and +Y axis of the crossHair
            crossHairX.setLeft(x - getWidth() - 1);
            crossHairX.setTop(y - getHeight() - 1);

            // crossHairY is +X, -Y
            crossHairY.setLeft(x);
            crossHairY.setTop(y);
        }
    }
}
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